Understanding Stem Cells

1. What are Stem Cells: The Origin of Life

What are stem cells? Stem cells are the building blocks of the human body. Each stem cell is capable of self-renewal by replicating to bolster its numbers, and differentiating into various cell types of the body. The combined effects of replication and differentiation is what allows a small number of stem cells to give rise to a human body that houses over 30 trillion cells. Over the course of natural human lifespan, the number of stem cells increases exponentially from conception to infancy. At this point of life, the large number of stem cells is required to shape the various organs that provide life-sustaining functions.

After the child is born and grows into adulthood, the number of stem cells in the body drops drastically as developmental changes have consumed that large number of stem cells. In adulthood, the stem cells present in the body are limited in their differentiation potential—their main duty is to maintain and repair bodily damage.

This small number of stem cells persists in the adult body until old age, when signs of aging progressively manifest. Symptoms like tremors, forgetfulness, and breathlessness are all due to weakening organs that, in turn, result from the lack of sufficient stem cells to carry out regeneration and repair.

Death eventually occurs, as there is no natural way to increase the number of stem cells in the body. The stem cells that once replicated vigorously have aged, and become less capable. The cells in the body will have to do without repair, and organs eventually fail. We are only as old as our stem cells.

2. Stem Cell and Regenerative Medicine

The stem cell replicates for a prolonged duration to create more stem cells that then differentiate into a cell type that the body needs. This chain of events elicits a powerful phenomenon where stem cells

repair

regenerate

replace

damaged or worn cells in the body.

When this power is harnessed for medical applications, their potential becomes greater than ever. This medical application is called regenerative medicine. Regenerative medicine can theoretically reverse degenerative conditions and increase lifespans by introducing a fresh supply of stem cells into the body.

3. Stem Cell Types

Despite their shared ability for self-renewal and differentiation, stem cells differ in the range of cells they can differentiate into. Pluripotent stem cells are those that can differentiate into any cell type of the body, while multipotent stem cells are usually restricted to the handful of cell types that make up and organ.

Pluripotent Stem Cells

Embryonic stem cells (ESC) that shape the human body from conception are pluripotent stem cells. Pluripotent stem cells must thus be capable of differentiating into all cell types of the body, such as nerves, skin cells, and even multipotent stem cells that give rise to blood cells and muscle cells.

Pluripotent stem cells have the greatest potential for medical application and, if successfully applied, will render multipotent stem cells obsolete for medical treatments as anything multipotent stem cells can do pluripotent stem cells can do better.

However, the medical application of pluripotent stem cells such as ESC is rife with controversy as the destruction of an embryo is required for their extraction.

Multipotent Stem Cells

Haematopoietic stem cells and mesenchymal stem cells are currently the most widely used multipotent stem cells stem cells for treatment. Despite their widespread application, their multipotency limits the range of disorders they can treat. This is compounded by complicated procedures and lengthy multipotent stem cell culture periods.

Haematopoietic Stem Cells (HSC)

Haematopoietic stem cells differentiate into blood components like white and red blood cells, and platelets, and are thus limited as they only treat blood disorders such as leukaemia. They are typically sourced from peripheral blood, bone marrow, or cord blood. Bone marrow haematopoietic stem cell procedures are invasive and surgical, and require compatibility testing between donor and patient to prevent the transplanted cells from being rejected. Peripheral blood extractions often yield low cell counts and will require genetic expansion to increase their numbers, resulting in an added mutation risk.

Mesenchymal Stem Cells (MSC)

Mesenchymal stem cells differentiate into structural cells of the body such as bone, cartilage, muscle, and fat. They are primarily used for sports and joint injuries, and suffer from similar technical caveats as haematopoietic stem cell procedures. However, Mesenchymal stem cells have an additional source from adipose tissue (body fat) that requires an invasive liposuction extraction, though this is not viable for underweight patients.

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